Tie cord



D. W. LIGHT July 18, 1961 TIE CORD Filed Oct. 10, 1958 Unite atent2,992,584 TIE CORD Donald W. Light, Groton, Mass., assignor to PepperellBraiding Company Incorporated, East Pepperell, Mass, a corporation ofMassachusetts Filed Oct. 10, 1958, Ser. No. 766,569

3 Claims. (Cl. 87-2) This invention relates to cord of the type thatmust be tied and untied frequently, and used for example, to adjust orbind articles of clothing or equipment, finding particular utility asshoe strings.

Tie cords currently are generally made by braiding textile yarns. Cottonyarns are most commonly used, but on occasion the braid yarns used havebeen made from filament or staple rayon or superpolyamidic fibers ormixture of these synthetic fibers with cotton, or elastic thread made ofa rubber core tightly wound with fine textile yarns, Of these, myexperience indicates that braided cotton cord has so far been thought tohave achieved an optimum balance between good knotting characteristicsand good wear characteristics, others, such as cords formed fromsuperpolyamides, being so slippery and incompressible as to have poorknot behaviour. Therefore, these last-named materials have not madegenerally satisfactory tie cords.

Cotton cords, particularly when used as shoe strings, are still subjectto much criticism due to breakage and coming untied at awkward moments.

My analysis of the essential desirable characteristics of cords, i.e.,long wear and good knot behaviour, shows that the two sets of propertiesrequired are to a large extent mutually opposed.

By good knot behaviour, I mean a knotthat is easily tied, will stay tiedthrough ordinary use, but which can nevertheless be readily untied. Tomeet these requirements a cord must be soft and flexible and easilycompressible, with high surface friction, still compatible with therequirement that it be capable of being readily untied whenever desired.On the other hand, long wear required high strength, endurance toflexing and resistance to chafing which in turn is improved by lowsurface friction. One cannot normally have low and high surface frictionat the same time and in general these two sets of properties are opposedso that treatment or change to improve one, degrades the other, and abalance must be sought at as high a quality level as possible.

I have discovered that a tie cord combining these deesirable andsomewhat mutually antagonistic qualities to a degree heretofore thoughtunobtainable, may he achieved, quite surprisingly, by using as a braidmaterial synthetic yarns which in their usual state are relatively hard,incompressible, and slippery, but which have been treated so that theirsurface characteristics yield improved qualities of flexibility andcompressibility and higher surface friction together with a quality ofstretch which is unexpectedly desirable and of a different characterfrom that afforded by rubber threads of the prior art.

In accordance with the present invention, I make my improved tie cord bybraiding permanently crimped superpolyamidic yarns in whih the filamentsare also permanently crimped. This braiding results in helicalarrangement of all the yarns with respet to the cord itself. While Iprefer using permanently crimped superpolyamidic twoply yarns ranging inweight from one hundred to two hundred ten denier per ply for use asshoe strings, I do not wish to limit myself to these weights or to thisparticular article because there are many other uses that can beadvantageously served by the combination of long wear and good knotbehaviour of my tie cord that may require a level of tension equilibriumdifferent from shoe strings and thereby a different range of yarn.Similarly, it is preferable for shoe strings to use thirty-two toeight-eight two-ply yarns in the braid. The braid construction musthowever be in proper balance to obtain maximum advantage from thepresence of the crimp. For shoe string use, picks per inch in theextended or stretched condition under one pound tension multiplied bythe square root of the total denier in a pick should be maintainedwithin the range of approximately 350 to 550.

Further objects, features and advantages of the invention will becomeapparent from the following detailed description of a preferredembodiment thereof taken in conjunction with the accompanying drawings,wherein like numerals refer to like parts in the several views and inwhich:

FIG. 1 is a perspective view of one end portion of a tipped braided tiecord, made in accordance with my invention, to illustrate itsappearance;

FIG. 2 is a plan view of some of the permanently crimped filaments inthe unstretched state, to show specifically the source of the increasedsurface friction and compressibility described above;

FIG. 3 is a magnified plan view of a portion of the improved tie cord inan unstretched condition; and

FIG. 4 is a view of the same similar to FIG. 3 but showing the cord in atensioned condition, illustrating the stretch effects.

Permanently crimped superpolyamides are utilized in this invention.There are various methods. of crimping to give different configurationsand character of crimp to superpolyamidic yarns and filaments, but thepreferred one is that described by L. A. Billion in his United StatesPatent No. 2,564,245, issued August 14, 1951.

Braid tightness is defined by the number of pick crossings per inch oflength along the braid. These are known in the trade as picks per incFor a given yarn material, tightness in a braid is a function of theproduct of the number of picks per inch and the square root of the totalweight of yarn in a pick in the braid. In the preferred embodiment of myinvention wherein the cord is used as a shoe string, with the weight ofyarn measured in denier, I have found that such product should bemaintained in the range of between about 350 to 550. Within these limitsa cord is produced having an excellent balance of long wear and goodknot behaviour, far exceeding the level of cotton or any other tie cordsknown tome. The crimp of the filaments and yarn increases the surfacefriction andcompressibility at the knot to give superior holdingproperties for knots that are nevertheless easy to tie but still untiereadily. The wear is not seriously impaired by crimping, and tests haveshown such a cord will wear over five times as long as a high qualitycotton cord that was twice as heavy.

As applied especially to shoe strings, the present inven' tion has afurther advantageous characteristic, one which was at first believed tobe a serious disadvantage in that the crimped filaments and yarns wouldbe expected to produce a stretchy braided tie cord. One would expectthis cord to have the serious disadvantages of known elastic shoestrings, including difficulty in lacing to the proper tension so theshoe would feel firm and secure without binding and ditficulty of tyingand untying the knots. Tests and field trials have shown, however, that,within the construction limits of the invention, the stretch due tofilament crimp is essentially all removed at the low tensions normallyused in lacing a shoe resulting in a tension in the lacing which I havefound to be close to the optimum for comfort and security. In fact, andhere is where the advantage of this particular type and quality ofstretch has appeared most strikingly, it was observed in field trialsthat the slight residual stretch or give remaining in the lacing in factincreased shoe comfort and the sense of secure footing. It was alsonoted that the loops and ends above the knot, being under no tension,retracted to a degree Where there was less likelihood of stepping andtripping on them while the free ends remained readily accessible to thegrasp for pulling the knot undone. Also the stretch characteristic wasnot such as to make tying in the least difficult.

Referring now to FIG. 1, it will be seen that the braided cord 4 whenprovided with an ordinary tip 2 presents a fine appearance suitable forall lacing applications.

In FIG. 2 there are shown crimped superpolyamide filaments which make upthe yarn. In FIG. 3 there is shown a section of braid in a relaxedcondition. A few filaments 5 are shown in each yarn 6 by way ofillustrating the nature of the yarn.

FIG. 4 illustrates the partial straightening of the crimp of thefilaments 5 comprising each yarn 6 and the change in character of thistie cord upon tensioning that enables it to combine the properties oflong wear with those for good knot behaviour.

In general, the braiding of my improved tie cord is accomplished onconventional braiding machinery but with particular care to maintainuniform tensions. It has been found advantageous to wet process afterbraiding to ensure uniformity of cord compression.

It will thus be seen that the invention resides in part at least in mydiscovery that the surface friction and compressibility of tie cordsmade of braided superpolyamidic filament yarns can be increased to anunexpected extent by permanently crimping the yarns and filaments priorto braiding, obtaining a balance of long wear and good knot behaviourproperties superior to any tie cords known to me. The invention furtherresides in my discovery that for use as shoe strings and the like such atie cord functions as two different cords: in the laced area where thestring is under some tension the properties contributing to long Wearpredominate, in the knot area, where there is no tension beyond theknot, the properties contributing to good knot behaviour predominatethusresolving the opposition of these two sets of properties. Further, foruse as shoe-strings, with such a tie cord construction Within the limitsdescribed above, I have found that the slight residual stretch in thelaced portion functions as an ad vantage instead of a disadvantage inthe tension adjustment and the comfort of the shoe whereas in theportion above the knot where there is no tension the retraction of theloops and ends contributes to the safety and neat appearance of theshoe.

While I have herein illustrated and described a presently preferred formof the invention, it will nevertheless be understood that the same issusceptible of modifications and changes by those skilled in the art,and that the invention is, therefore, intended to be limited only by theproper scope to be afforded to the appended claims.

I claim:

1. A cord for securing articles to living beings, adapted to be tied anduntied, said cord having a two phase stretch, the first 'of which is aready stretch and compressibility pulled out at low tensions, and thesecond of which is a residual lesser stretch of a noticeably dilferentmagnitude and character in which phase the cord exists under normaltying tension, said cord being comprised of braided synthetic crimpedyarn, and said cord having increased surface friction With its outersurface defined by exposedv portions of said braided yarn, the secondresidual stretch providing a further yielding and tension adjustment ofthe cord when under normal tying tension in response to the increasedstress attributable to the wearer, said cord being easily tied into aknot and holding the knot during active use while still being capable ofbeing readily intentionally untied, said knot holding being augmented bysaid surface friction and by said compressibility, and the free,untensioned loops and ends of said cord being contracted by virtue ofsaid first ready stretch.

2. A cord as claimed in claim 1 in which the synthetic crimped yarn is asuperpolyamide.

3. A cord as claimed in claim 2 for use as a shoe string in which thepicks per inch of its length in the extended or stretched conditionunder one pound tension multiplied by the square root of the totaldenier in a pick is maintained within the range of about 350 to 550.

References Cited in the file of this patent UNITED STATES PATENTS1,948,844 Dawes Feb. 27, 1934 2,099,016 Houghton Nov. 16, 1937 2,477,151Stapleton July 26, 1949 2,564,245 Billion Aug. 14, 1951 2,715,309Rosenstein et al Aug. 16, 1955 2,815,559 Robinson Dec. 10, 19572,841,046 Runton July 1, 1958 2,846,840 Billion Aug. 12, 1958 2,887,005Fromm May 19, 1959 FOREIGN PATENTS 909,448 France Dec. 20, 1945

